In U.S. Pat. No. 5,030,890 entitled "Two Terminal Incandescent Lamp Controller" issued Jul. 9, 1991, there are disclosed and claimed new and useful improvements in the field of controlling various lighting functions of an incandescent lamp bulb, such as timing, duty cycle control, dimming and illumination intensity. This two terminal incandescent lamp controller is operative to provide in memory certain data values corresponding to the timing or sequence at which power interruptions to the memory may occur. Timed or sequenced power interruptions to the memory are created in order to select a particular data value for storage in memory which is then operative to control either the conduction time, the duty cycle, or the illumination intensity of the lamp bulb. This conduction time, duty cycle, or illumination intensity control is achieved by connecting an AC triggerable switch, such as a TRIAC, to the lamp and controlling its conductive state by the application thereto of the particular data value selected for storage in the memory of a microprocessor.
In a subsequent commonly assigned U.S. Pat. No. 5,126,634 entitled "Electronic Control Module (ECM) for Controlling Lighting Functions of a Lamp Bulb and Method of Manufacture" there are disclosed and claimed further new and useful improvements in the field of lamp bulb function control. These improvements include, among other things, a new and improved process for manufacturing a circuit integrated and controlled light bulb. This manufacturing process includes the steps of providing a light bulb having a filament wire therein and a dielectric insulator at one end of the bulb, with the insulator having a recessed cavity adjacent to which an opening extends to an interior section of the bulb. An electronic control module (ECM) is mounted in this receptacle and then connected to a filament wire of the bulb for thereby controlling one or a plurality of bulb lighting functions in response to the operation of the electronic control module.
In yet a subsequently filed and commonly assigned U.S. application Ser. No. 07/847,179 entitled "Lamp Bulb With Integrated Bulb Control Circuitry and Method of Manufacture" filed Mar. 9, 1992, now U.S. Pat. No. 5,214,354, there are disclosed and claimed yet still further new and useful improvements in the field of electronic control module design wherein a new and improved ECM article of manufacture is constructed having a metal housing with a base or floor member being surrounded by an upstanding wall member defining an opening in the housing. A ceramic substrate is mounted on the base member, and bulb lighting control circuitry is constructed on the substrate and has a conductive bridge member connected thereto for transmitting control signals from a microprocessor in the bulb lighting control circuitry to the filament of a light bulb. This application and the above two patents preceding it are incorporated herein by reference.
Whereas the above identified inventions represent most significant advances in the fields of lamp bulb manufacture and associated lighting function control, the operation of the TRIAC in the ECM module in response to microprocessor controlled input signals can, in some cases, generate undesirable radio frequency interference (RFI) radiation. This RFI is generated as a result of the steep di/dt rise time due to the TRIAC turn-on from voltage on each one-half cycle of the AC line voltage which is applied across the anode and cathode terminals of the TRIAC. This undesirable radio frequency interference can be radiated as RF signals from the lamp bulb acting as an antenna and into the surrounding ambient, and it can also be transmitted directly back through the AC line voltage source to thus provide electrical interference to other appliances connected to this same source of AC voltage. In either case, this radio frequency interference is undesirable and may in some cases exceed acceptable electrical code levels for RFI in certain countries.